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Ikea 'Solvinden' - Solar USB Power Supply

This is yet another solar power supply instructable. But wait! What makes this one different?

Well for starters, it only costs about $10 and can power most USB devices.

But the major feature is that it has the sweet Swedish IKEA styling and functionality that everyone enjoys.

Once we're done, you'll hardly be be able to tell that anyone has been into it.

Sturdy and weather resistant and there is enough cable supplied in the original IKEA kit to run from your sunny location to where ever you need the power.

Step 1: Step 1: What You'll Need

1) IKEA Solvendin Solar Party Lights

These little kits are great. I got them for $5 on special. It includes a 7-8V solar panel, 2 rechargeable 1.2 v NiMH batteries, some little plastic lanterns and a string of LEDs on about 10 meters of cable. The big benefit, it that's it's actually well put together. I've had a set outside for a while now and they've kept going. The seals around the solar panel provide good weather protection and the cable is fairly rugged.

Of course, the 2 rechargeable 1.2 v NiMH batteries are pretty weak, but what do you expect for $5? They can be replaced with something better if you like down the track. In this build, I haven't bothered with overcharge protection so I'm willing to sacrifice the batteries.

2) DC-DC USB 0.9V-5V to 5V dc Boost Step-up Power Supply Module

Essentially, this little board converts 0.9 - 5 V power supplies up to a steady 5V DC output through a built-in female USB.

3) A housing for the USB Power Supply Module. I used a spare battery holder. It has a built in switch and can be sealed up nicely.

4) A diode. I used a 1N4742 ZENER Diode 1W 12V. But anything over 9V should be fine. It's only there to make sure we don't have power leakage.

5) Some spare wire and soldering tool.

Step 2: Step 2: Opening the Panel

The great thing about this hack is you could use the panel "as is". Allowing it to charge up during the day and providing power at night to the separate USB power module. However, this isn't what I wanted.

The PCB built into the panel is very frugal with it's power supply to give you a long time with the LED lights on. It also seems that the whole panel needs to be covered to supply power, unlike most older solar garden lights which have a photoresistor. I decided to open the panel and "fix" this problem.

To open the panel, just insert a blade (here using my swiss army knife) along the seam and lever it up. It should pop open. Work your way around until it comes off.

Remember Safety first!

Next, unscrew the one screw holding the board in place and cut out the PCB out. Trim the wires back but keep as much as you feel necessary to give you room to solder and re-wire the board.

Step 3: Step 3: Diode(s)

Diodes are important components to make sure electricity only travels one one.

In this version, I've soldered the diode directly to the panel. This ensures we only have current moving in the correct way across the panel to prevent power leakage when the sun's not out. Make sure you check the polarity before soldering!

In a later version of this instructable, I'll include overcharge safety.

Step 4: Step 3: Wiring the Panel

This is where it might get tricky.

First solder the battery +ve to the solar panel +ve and the battery -ve to the solar panel -ve. This will charge the battery when the solar panel is exposed to light. The diode we added previously will prevent current flowing back across the solar panel.

Connect the shared -ve to the -ve of the cable (the wire without the spots)

Then connect the shared +ve to the switch, then from the switch to the +ve of the cable (the wire with spots)

See the circuit diagram if you feel you need it.

Step 5: Step X: Cable and USB Power Module Housing

Now that you have the solar panel wired up and fitted back together, onto the cable and USB power module!

The Solvinden Kit comes with a cable with a nice plug and several LEDs. We'll use this to give our panel extra reach. There is about 5 m of cable before the first LED so cut it as long as you like. The cable itself is just two separately insulated wires so you'll have no trouble doing this. Take note of the cable and you'll notice one wire has a dashed white line on the outside. This is +Ve (at least in my case) and it's important since the plug will ensure only a certain polarity will work. If nothings working at the end, look into which way you have these two wires around.

To house the module I used a small 3 AA battery housing. It had a built in switch and was just big enough to fit the board. Simply wire up the cable coming from the panel to the board (+Ve on the cable has a dash along it, -ve no dash).

You could always use the USB slot built onto the board and cut a hole in the housing to fit it through, but I didn't feel up to cutting the housing too much. Instead, I've just plugged an extendable USB cable into the board, cut a little hole in the housing to feed it through, and left the rest hanging out. It fits nice and snugly and it won't damage the board if the cable is pulled.

With this housing too, you can see where I've soldered up the switch to the board and the cable. Just put the switch inline with the +ve wire and you'll be fine.

That's pretty much all you need to do here.

Step 6: Step 6: Putting It All Together and Powering Up

With the last step done, put everything back together, plug it all together and put it out in the sun to charge up.

As you can see here, our little Solvinden hacked solar lamp is powering a desktop USB fan.

It works well for uses like this such as fans and small radios. However, I would be careful using it for charging your phone. I can't guarantee the output from the USB power supply module is stable and like all "non-standard" chargers, continued use may harm your device's battery.

However, in an emergency, it could be handy!

I'll upload some more pictures later when I get a chance to use it while "off-grid" on the weekend.

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3 Discussions

As you allready wrote, this is just another solar to USB project. Nothig fancy, but cheap. It doesn't contain any battery protection (over- and undervoltage, overtemperature), but you mentioned that. I like the contractible USB extension cord, haven't seen that before. In my experience they thend to break quite easy, so take care when handling it. I'd prefere everything in one unit, because it reduces the mess of cables. It would also improve the efficiency a little bit, because there wouldn't be a loss due the resistance of the cable. Speaking of losses the diode you picked is a poor choice. Zener diodes are meant to be used in reverse to cause a stable, fairly precise (5-1% accuracy) voltage drop. Typically a simple 1N 4007 (0.02€) diode would be used. For a better efficiency you should pick a shottky diode (such as the 1N 5817/5818, 0.06€), it has a lower forward voltage and therefore burns less power. In this example it would be 0.45V (1N 5817) instead of 0.9V (1N 4007) @1A, so half the loss and around 5% better overall efficiency.

The idea behind having such a long cable was so I can leave it outside and have power into the shed where we've been camping at night. The contractible USB extension and the diode choice was just what I had at hand.

Since this one seems to work pretty well in the field, I'll review the component choices for my next one to improve efficiency like you suggested as well as include overcharge protection.